This invention relates generally to contact lenses and specifically to a completely novel type of contact lens that can be molded and/or altered by the pressure of the eyelids when in the act of attempting to accommodate or “focus”. That is, to change the refractive status of the eye such as when trying to clearly visualize objects at different distances, such as from far to near (i.e. accommodation).
In a normal condition, light from the distance (standardly considered 20 feet or more) enters the eye as parallel rays and is brought into a clear image by the optical components of the eye (primarily cornea and lens) to focus on the retina for an emmetropic or refractively corrected (such as with spectacles or contact lenses) eye. This is when the eye is in a relaxed condition, or unaccommodated state. However, when objects are viewed within 20 feet, light from the objects are divergent and a change in power of the same eye is needed to bring these rays into focus. For a person who is phakic (retaining their natural intraocular lens) and pre-presbyopic (still having the ability to accommodate or focus), they can simply rely on their natural physiological focusing ability to adjust the power of their eye (add power) to bring the near light rays into focus. This process involves the contraction of the ciliary body, relaxation of the lens zonules and a change in the shape of the intraocular lens to provide this additional power. This process of changing dioptric power to the eye is called accommodation and diminishes throughout life, but most noticeably after the age of 40 years old until the ability is essentially gone after about age 50 years old, in a condition called presbyopia (Charman 2008).
Currently, several proposed surgical “treatments” for presbyopia are quite invasive and produce irreversible physical changes to the eye. They often require implantation of an artificial intraocular lens that may or may not move with accommodative effort, or implantation of artificial bands in or around the eye, such as with scleral bands, which have not been successful in providing adequate accommodative amplitudes to the presbyopic eye for clear and stable near vision (Glasser 2008).
A more non-invasive, reversible method of alleviating the accommodative deficiency of the eye due to presbyopia are in either spectacle correction with an add, or through various forms of contact lenses, such as with multifocal lenses; or contact lens wearing methods, such as with monovision. These contact lens treatments function by providing pseudoaccommodation with a multifocal or aspheric design (Bennett 2008). However, all of these designs rely on a static contact lens and particularly a static contact lens and eye interaction.
The cornea provides a majority of the refractive power of the eye, but remains relatively stable during accommodation attempts as it is primarily the intraocular lens that produces the most change in shape and subsequently refractive power (Charman 2008). However, studies have shown that the cornea is malleable and does show a small change in shape, with consequent change in refractive power when the eye is accommodating (Pierscionek et al. 2001, yasuda et al. 2003) and after extended periods of reading or near work (Buehren et al. 2003), but will return to its normal state after the end of the accommodation or near viewing effort. It has also been shown that the pressure from the eyelids during this accommodative process is the primary cause of corneal shape change (Buehren et al. 2003).
This invention is stated to provide some level of active accommodation (change in refractive state when viewing from far to near) to the eye by having the wearer change the shape and position of the contact lens, and additionally the tear layer beneath the contact lens, with the pressure of their eyelids during attempts to focus at near, thereby increasing the power to the eye and bringing near objects into focus.